Acoustic horn and method of manufacture thereof



Sept. 20, 1932. ABRAHAMS l 1,878,360

ACOUSTIC HORN AND METHOD OF MANUFACTURE THEREOF Filed Sept. 26. 1951 INVENTO R A lxandr T A b raham 3.

BY his ATTORNEY): jg

Patented Sept. 20, 1932 PATENT OFFICE ALEXANDER I. ABBAHAMS, OF NEW YORK, N. Y.

ACOUSTIC HORN AND METHOD OF MANUFACTURE THEREOF Application filed September 26, 1931.

This invention relates in general to improvements in the method of manufacturing acoustic horns, and the product itself.

The more specific objects of the invention are to provide acoustic horns of the type made up of reinforced fabrics which are particularly suitable for outdoor use.

A further object is to provide horns of this nature which are strong, rigid and form sustaining, and which are particularly moisture repellent to the extent that they may be directly subjected to water without affecting their structure.

A still further object is to provide a horn of this type in which the walls thereof are of such rigidity that they are not set in vibration, and hence act as sound amplifiers and directors without introducing undesired sounds into the sounds being amplified and directed.

Another object of this invention is to provide a horn of this type comprised of at least one, and preferably two or more, layers of deep pile fabric or knitted fabric stretchable in all directions and impregnated with a hardening compound which is not water soluble.

A feature of the invention relates to the method of manufacturing an acoustic horn without subjecting the horn material to pressure during the shaping or molding thereof. As a result of this feature the final horn has the requisite rigidity to enable it to act as an efficient radiator, and at the same time is free from the undesirable effects of so-called pressure molded horns such as brittleness or the like.

These and other objects are obtained by means of this invention, as will appear from the following disclosure.

This invention resides substantially in the combination, construction, arrangement, relative location of parts, steps and series of steps in accordance with the following detail disclosure.

Referring to the drawing:

Fig. 1 is an elevational view of a horn employing this invention with a portion broken away; and

Fig. 2 is a cross sectional view through the wall of the horn.

A fabric such as a knitted or woven cloth Serial No. 565,297.

having preferably, although not necessarily, a deep pile, and which is stretchable in all directions is employed in making the horn. Two or more thicknesses of this fabric are employed and the nap is preferably, but not necessarily, brushed up to increase the pile of the fabric. The first fabric is preferably cut to the desired shape and is then impregnated in any well known manner with a waterproof varnish, for example by dipping, rubbing the varnish in by hand, or in any other suitable manner. The second piece of fabric is similarly cut and is placed over the first fabric, and is likewise impregnated with a water-proof or water insoluble varnish. It is preferred to superpose the fabrics in such a manner that their piles intermesh. Instead of impregnating each of the fabrics separately and then superposing one on the other the fabrics may be superposed with their piles inter-meshing and then impregnated by dipping them in a water-proof or water insoluble varnish, after which the impregnated fabrics may be placed over a suitable form or mold corresponding to the shape of horn desired. The water insoluble varnish used for impregnating the fabrics is preferably of the type having a base of cashew oil combined with driers such as formaldehyde or manganese oxide all dissolved in a suitable hydrocarbon. Such a varnish has practically solids, and is very little oxidized upon exposure. The above type of varnish is given by way of example, and other types can be employed such as a high grade spar varnish which has a base of resin or gum dissolved in oil. The important characteristics required of the varnish is that it be insoluble in water so that the horn impregnated therewith may be directly exposed to the atmosphere and to water.

After the fabric has been impregnated with water-proof varnish the said varnish may be subjected to a drying or baking operation, for example, the mold or form containing the impregnated fabric may be dried in a heated oven or the like, or it may simply be allowed to dry in the open air; or if desired, a quick drying water insoluble varnish may be employed. In any event, it is preferred, in accordance with this invention, to effect the drying operation under normal atmospheric pressure since it has been found that the final product obtained in this manner exhibits the optimum self-sustaining rigidity to enable it to act efiiciently as a sound radiator while at the same time the material does not possess marked brittleness which is an unavoidable concomitant when the product is formed by a pressure or molding method.

The pieces of fabric are suitably shaped and secured together to provide the neck 1 of a horn and the bell 2. As shown in the drawing, the horn as illustrated is made up of two pieces of fabric 3 superimposed on one another so that the nap of each piece interlocks with the other as indicated at The fabric is then stretched upon a suitable form, depending on the shape that is desired for the finished product. The fabric in accordance with this invention is cut and sewed to form a base or blank similar to a stocking so that it may be stretched over a suitable form such as metal or the like, in which case the form may be made in removable sections so that when the fabric is finally baked and dried the sections of the form may be expeditiously removed. In other words the fabric base is cut in what may be termed a blank corresponding to the shape of horn desired and the fabric may then be stretched around the form and sewed, or if desired the sewing may take place first and then the sewed blank in stocking form may be stretched over the mold.

This manner of forming the horn is of decided advantage where horns of large dimensions are to be made, since it has been found that ordinary pressure methods of molding the horn and the molds themselves are extremely costly, and unless very careful precautions are taken a non-uniform product is obtained. Furthermore, by using an internal form and positioning the horn fabric on the exterior thereof very large horns may be made in accordance with this invention with absolute uniformity in product, and at very low cost. By employing a fabric which is stretchable in all directions it is possible to accurately fit the fabric onto the form to give a smooth regular shape.

Any well known method of impregnating the fabric with water insoluble varnish may be employed, it being understood, however that such impregnation is preferably effect-ed under normal atmospheric pressure. For example, after the fabric is stretched onto the form, it may be impregnated by spraying, brushing, pouring, or in any other well known manner. Or if desired, the fabric may be dipped into a quantity of the impregnating varnish, care being taken to remove the excess material. In the case of impregnation by dipping, of course, it is preferable to achieve the impregnation prior to the application of the material on the form. It will be understood, of course, that each individual layer of fabric may be separately impregnated, or if desired, the complete fabric assembly may be impregnated as a unit. The impregnated fabric while on the form is dried preferably in the open air, or at least under normal pressure. This drying may be effected by heating or by employing a varnish that is self drying.

After the baking operation the form which is preferably made in sections is disassembled,leaving an accurately shaped horn which possesses the requisite firmness, rigidity and hardness, and which is water-proof and weather-proof. Furthermore, by this method of using an interior mold, any other complicated shapes may be very readily manufactured with absolute uniformity of results. The resulting horn is strong and rigid. The fabric by reason of its impregnation with the water-proof varnish is covered inside and outside with a. smooth dense coating as indicated at G. If desired, the finished horn may be further coated with the same varnish to give a smooth hard finish.

\Vhile it has been found that the best re sults are achieved when pile fabrics are employed as the horn base, it will be understood that certain advantages of the invention are achieved with other materials, for example, the horn may be formed out of a knitted fabric with a pile surface or out of absorbent paper. In the case of paper, however, since it is very difficult to stretch or sew the paper over the form, the horn may be built up in overlapped sectional paper strips, care being taken to impregnate each layer as it is placed on the form, after which the impregnated paper material may be baked as above described.

The horn of this invention is of particular use in outdoor installations, and can be subjected practically to all kinds of weather conditions including rain, without danger of absorption of water and a resulting softening of the walls, Thus, even when the horn is exposed to water the walls do not soften so that the horn maintains its shape and the walls thereof remain strong and rigid so that they do not interfere with the proper acoustic action of the horn.

From the above disclosure it will be apparent that the method and product thereof comprising this invention may be effected in other ways by those skilled in the art, and I do not, therefore, desire to be strictly limit-- ed to the disclosure as given for purpose of illustration, but rather to the scope of the appended claims.

\Vhat I seek to secure by United States Letters Patent is:

1. A water-proof horn of the type described comprising a base formed of textile fabric of the deslred size and shape thoroughly impregnated with a hardened varnish insoluble in water.

2. A horn of the type described comprising a preformed base of textile fabric of the desired size and shape impregnated with a hardened filler of water-proof varnish having a cashew oil base.

3. A horn of the type described comprising a preformed base of textile fabric of the desired size and shape impregnated with a hardened filler of Water-proof varnish having a cashew oil base mixed with a drier and a solvent.

4. A horn of the type described comprising a. preformed base of at least two layers of a deep pile fabric thoroughly impregnated in a water insoluble varnish, the layers of fabric being arranged so that the pile of each interlocks.

5. A horn of the type described comprising a preformed fabric base made up of at least two layers of a deep pile fabric stretchable in all directions and thoroughly impregnated with a hardened water insoluble varnish.

6. A horn of the type described comprising a knitted fabric base of superimposed fabric layers formed to the desired size and shape and thoroughly impregnated throughout, and coated on both surfaces and cement ed together with a water insoluble varnish.

7. The method of manufacturing a horn of the type described, comprising the steps of providing at least two pieces of deep pile fabric of the desired shape, thoroughly impregnating the two pieces of fabric with a water insoluble varnish, superimposing the two pieces of fabric with the pile of each in contact, stretching the superimposed pieces of fabric over a form and baking them.

8. The method of manufacturing a horn of the type described, comprising the steps of providing at least two pieces of knitted fabric cut to the desired shape, thoroughly impregnating the fabric with a water insoluble varnish, stretching the fabric in superposed relation over a form and baking said fabrics while on the form.

9. The method of manufacturing a horn of the type described comprising the steps of providing at least two pieces of knitted fabric of the desired size and shape, stretching one fabric over a form, superposing and also stretching the other fabric over the first fabric on the form, both of said fabrics being impregnated with a water insoluble varnish, and baking the superposed fabrics at atmosa pheric pressure in their stretched condition on said form.

10. The method of manufacturing an acoustic horn of the type described comprising the steps of stretching a textile fabric over a form, impregnating the fabric without pressure with a water insoluble varnish,-

and allowing said impregnated textile to thoroughly dry.

11. The method of manufacturing an acoustic horn which includes the steps of cutting a textile fabric to form a horn blank, sewing said blank to provide a stocking-like member, stretching said member over a form, impregnating said member with a water insoluble varnish, drying said varnish, and then removing the sectional form.

12. The method of manufacturing an acoustic horn of the character described which includes the steps of stretching a stocking-like fabric over a form, impregnating said fabric with a water insoluble varnish while on said form, stretching another layer of fabric over the first mentioned fabric, and impregnating the second mentioned fabric with a water insoluble varnish, baking both said impregnated fabrics, and then removing the form sections without disturbing the fabrics.

In testimony whereof I have hereunto set my hand on this 24th day of Sept, A. D.

ALEXANDER I. ABRAHAMS. 

